It now appears that polyisoprenyl phosphates may participate as activated glycosyl carriers in the assembly of oligosaccharide chains of some membrane glycoproteins in animal tissues. This mechanism is analogous to the role of polyisoprenol intermediates in the biosynthesis of complex polysaccharides of bacterial cell envelopes. The research plan described in this proposal includes a study of the biosynthesis and structure of the polyisoprenol-linked glycosyl intermediates formed by membranous fractions prepared from bovine brain. Their function in the biosynthesis of brain membrane glycoproteins will also be investigated. One specific goal will be to determine if oligosaccharide units of some brain membrane glycoproteins are assembled at the lipid-level, and subsequently transferred to membrane protein acceptors. The distribution of lipid-mediated glycosyltransferases in several brain cell-types will be examined. The membrane glycoproteins glycosylated by lipid-mediated glycosyltransferases, in the various brain cell-types, will be characterized. Of particular interest, is the possible involvement of polyisoprenol intermediates in glycoprotein biosynthesis in oligodendrocyte membranes. This finding might be an indication that glycoproteins of the myelin membrane are glycosylated via lipid intermediates. If evidence is obtained supporting this hypothesis, a study of the possible correlation of the expression of the lipid-mediated glycosyltransferases with the myelination process will be conducted.